1. Field of the Invention
The present invention relates to an exposure apparatus and a device manufacturing method. More particularly, the present invention relates to an exposure apparatus used to manufacture semiconductor devices and liquid crystal display devices in a lithographic process, and a device manufacturing method using the exposure apparatus.
2. Description of the Related Art
Conventionally, in a lithographic process to manufacture devices such as semiconductors and liquid crystal displays, projection exposure apparatus has been used to project and transfer a pattern formed on a mask or a reticle (to be generically referred to as a xe2x80x9creticlexe2x80x9d hereinafter) onto a substrate such as a wafer or a glass plate (to be suitably referred to as a xe2x80x9csubstratexe2x80x9d or a xe2x80x9cwaferxe2x80x9d hereinafter) coated with a photo resist or the like. As an apparatus of this type, for example, in a manufacturing process for semiconductor devices, a static type (also referred to as a step-and-repeat type) exposure apparatus has been the mainstream. This exposure apparatus mounts a wafer as a substrate on a wafer stage, and after stepping the wafer stage by a predetermined amount XY in a two-dimensional direction, the reticle pattern is transferred onto a shot area on the substrate through an projection optical system. However, as the degree of integration increases in semiconductor devices and the circuit pattern becoming extremely fine, requirements for a higher resolution and exposure preciseness in the performance of exposure apparatus are also increasing. To meet these demands, in recent years, as an exposure apparatus employing a new method, the scanning type exposure apparatus based on a so-called step-and-scan method is becoming widely used. With this type of exposure apparatus, the wafer is illuminated with a slit-shaped illumination light through the reticle and the projection optical system. And along a direction perpendicular to the longitudinal direction of the illumination area of the illumination light, the reticle stage holding the reticle and the wafer stage holding the wafer are moved relatively with respect to the projection optical system, thus the reticle pattern being sequentially transferred onto the wafer.
With the scanning type exposure apparatus described above, when transferring the reticle pattern onto a shot area on the wafer, that is, on exposure, just before performing the exposure the positional information (focus information) of the wafer surface to the optical axis direction of the projection optical system is measured. The information is measured with a focus sensor at the exposure position (the shot area which is subject to exposure). And, scanning exposure is to be performed by positioning a sample holder (Z stage) holding the wafer which finely moves along the optical axis direction so that the surface of the shot area on the wafer coincides within the range of the depth of focus of the projection optical system.
With such a scanning type exposure apparatus, the focus information of the wafer just prior to exposure regarding shot areas excluding the circumferential shot areas of the wafer can be easily detected, therefore do not cause any problems. When exposing circumferential shot areas of the wafer, however, detecting focus information prior to exposure was often difficult, especially when an exposure area, conjugate with an illumination area of the reticle, was exposed with the relative scanning direction proceeding from the circumferential portion of the wafer to the center (the actual exposure is performed with the exposure area fixed and the wafer moving, however, the expressions above are used for the sake of convenience). In such a case, the Z stage movement lagged behind, thus, the reticle pattern was at times, transferred onto the shot area in a defocused state.
Meanwhile, in order to prevent the defocused state, a method is used in some cases where the scanning direction for the circumferential shot areas always proceed from the center of the wafer to the circumferential portion. However, in such a case, since the reticle and the wafer is always relatively scanned in a determined direction, the reticle stage and the wafer stage need to be restored to their original position. This naturally leads to a decrease in the throughput compared with when scanning exposure is performed alternately, to and fro, between one side of the scanning direction and the other side of the scanning direction.
Also, even if the circumferential shot areas were exposed with the scanning direction for the circumferential shot areas proceeding from the center of the wafer to the circumferential portion at all times, the detection points of the focus sensor did not entirely cover the wafer. Consequently, on some of the shot areas, the tilt of the wafer could not be adjusted, resulting at times in a pattern of a defocused state being transferred.
The present invention has been made in consideration of this situation, and has as its first object to provide an exposure apparatus that is capable of effectively suppressing the critical dimension variation by a macroscopic observation, which is caused by defocus during exposure.
It is the second object of the present invention to provide a device manufacturing method that can contribute to improving the productivity when microdevices with degree of high integration are produced.
With the scanning exposure apparatus, the substrate is relatively scanned with respect to the illumination area that is longitudinal in the non-scanning direction and transversal in the scanning direction. Therefore, in the case of any tilt error of the substrate surface in the scanning direction (pitching) to the image plane of the projection optical system, the contrast of the image transferred decreases, however, due to the averaging effect, defocus is suppressed at a moderate level. On the other hand, when there is a tilt error of the substrate surface in the non-scanning direction (rolling) to the image plane of the projection optical system, this directly becomes the cause of defocus. That is, the influence of the pitching and the rolling of the substrate on the exposure accuracy are not the same. The present invention has focused on this point, therefore has employed the following composition.
According to the first aspect of the present invention, there is provided a first exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the substrate projection optical system, the exposure apparatus comprising: a focus detection system which detects positional information on the substrate surface in an optical axis direction of the projection optical system at a plurality of detection points; a selection unit capable to set a selection criteria and select detection points according to the selection criteria, the selection criteria including a first type detection point selection criteria to control a tilt of the substrate in a moving direction and a tilt of the substrate in a direction perpendicular to the moving direction, the moving direction being a first direction whereas the direction perpendicular being a second direction, and a second type detection point selection criteria to control the tilt of the substrate with priority on the second direction; and a substrate driving unit which controls a position of the substrate in the optical axis direction and a tilt with respect to a surface perpendicular to the optical axis to adjust a positional relationship between the substrate surface within an illumination area and an image plane of the projection optical system based on positional information of the substrate surface in an optical axis direction of the projection optical system at the detection points selected.
With this apparatus, when the first type detection point selection criteria is set, according to the selection criteria, the selection unit selects a plurality of detection points to control the tilt of the substrate in the first direction and in the second direction. The first direction in this case, is the substrate moving direction during scanning exposure, and the second direction is the direction perpendicular to the first direction. And when the second type detection point selection criteria is set, the priority of control is on the tilt of the substrate in the second direction, and thus the appropriate detection points are selected. On exposure, that is, when transferring the mask pattern onto the shot area on the substrate, the substrate driving unit controls the tilt of the substrate to the optical axis direction and the surface perpendicular to the optical axis. By this control, the positional relationship between the substrate surface within an illumination area and an image plane of the projection optical system is adjusted, based on positional information of the substrate surface in an optical axis direction of the projection optical system at the detection points selected. As a consequence, when the first type detection point selection criteria is set, on exposure, the position of the substrate in the optical axis direction, the tilt in the first direction (pitching), and the tilt in the second direction (rolling) are adjusted. By this adjustment, the illumination area on the substrate, which changes corresponding to the relative scanning of the mask and substrate, is always within a predetermined depth of focus of the image plane of the projection optical system. Also, in the case the second type detection point selection criteria is set on exposure, the position of the substrate in the optical axis direction and the tilt in the second direction (rolling) are adjusted. By this adjustment, the position in the optical axis direction and the tilt in the second direction (non-scanning direction) of the illumination area on the substrate, which changes corresponding to the relative scanning of the mask and substrate, is always within a permissive amount (within a range where an excessive amount of defocus does not occur). Accordingly, it becomes to possible to precisely adjust the position of the substrate surface in the optical axis direction as well as the rolling, which greatly affect defocus; therefore, it becomes possible to prevent the critical dimension variation by a macroscopic observation, which is caused by defocus on exposure. In this case, regardless of the type of detection point selection criteria set, that is, the first type or the second type, so long as the position of the substrate in the optical axis direction (Z) and the rolling, and in some cases the pitching can be adjusted, alternate scanning can be performed on the entire shot area on the substrate, including the circumferential portion, thus allowing extremely high throughput to be maintained.
In this case, as long as the selection unit chooses the detection points in accordance with the criteria described above, the selection unit may use any method, for example, the selection unit can perform selection of the detection points in accordance with a size of a shot area subject to exposure. In such a case, for example, it is preferable to select detection points in the shot area where the interval between the detection points is at a maximum width in the second direction (non-scanning direction) as detection points in the second direction on both sides. This consequently allows the rolling of the substrate to be precisely detected as much as possible.
With the first apparatus in the present invention, as described above, on selecting detection points of a shot area subject to exposure according to its size, for example, when the shot area subject to exposure is an outward shot, the selection unit can select the detection points located within an effective area of the substrate at a judgement position where a rear-edge of the illumination area coincides with a fore-edge on the shot area directly after starting exposure based on a shot map prepared in advance. In this description, the xe2x80x9cfore-edgexe2x80x9d is used to specify the side of edge in the scanning direction when the illumination area is relatively scanned with respect to the shot area, and the xe2x80x9crear-edgexe2x80x9d refers to the edge opposite to the fore-edge.
In this description, an xe2x80x9coutward shotxe2x80x9d refers to a shot area where an axis extending in the non-scanning direction (the second direction) which passes through the center of the scanning direction (the first direction) of the substrate serves as a reference axis, and the illumination area is relatively scanned from the reference axis toward the circumferential portion of the substrate (in actual, the illumination area is fixed and the substrate moves, however, it is described as such for the sake of convenience).
With such an outward shot, by selecting the detection points within the effective area of the substrate at the judgement point, even if the shot area subject to exposure is a chipped shot, the most appropriate detection points can be selected to control the rolling of the substrate.
In this description, a xe2x80x9cchipped shotxe2x80x9d refers to a shot area other than a full shot. A xe2x80x9cfull shotxe2x80x9d is a shot area that includes a first position (coinciding with the judgement position) where the edge (rear-edge) on the exposure area IA coincides with the edge (fore-edge) on the shot area directly after starting exposure. It also includes a second position where the edge (fore-edge) on the exposure area IA coincides with the edge (rear-edge) on the shot area. The full shot area is in between these positions, and the detection points that are within the width of the second direction (non-scanning direction) which interval between the points is maximum, are the detection points in the second direction. These basic detection points, in the case of a full shot, are all located within the effective area of the substrate.
The definition of the effective area of the substrate may vary, however, in this description, the xe2x80x9ceffective area of the substratexe2x80x9d refers to the inner area of the disable range (almost matches with inner portion of the area usually arranged on the circumferential portion of the wafer where a pattern cannot be transferred) that is set as; xe2x80x9cedge bead remover width of the substrate +a margin around several mmxe2x80x9d.
Also, in the case of selecting the detection points based on the size of the shot area subject to exposure, for example, when the shot area subject to exposure is an inward shot, the selection unit can select the detection points located within an effective area of the substrate at a judgement position where a fore-edge of the illumination area coincides with a rear-edge on the shot area just before completing exposure based on a shot map prepared in advance.
In this description, an xe2x80x9cinward shotxe2x80x9d refers to a shot area where the direction of relative scanning of the illumination area to the substrate is opposite to the outward shot described above. That is, the illumination area is relatively scanned from the circumferential portion of the substrate toward the reference axis (in actual, the illumination area is fixed and the substrate moves, however, it is described as such for the sake of convenience).
With such an inward shot, by selecting the detection points within the effective area of the substrate at the judgement point, even if the shot area subject to exposure is a chipped shot, the most appropriate detection points can be selected to control the rolling of the substrate.
And, in the case of selecting the detection points based on the size of the shot area subject to exposure, for example, when the shot area subject to exposure is other than an inward shot and an outward shot, the selection unit can select the detection points located within an effective area of the substrate at a judgement position where the illumination area is located almost at a center in the first direction of the shot area subject to exposure based on a shot map prepared in advance.
With such a shot area, by selecting the detection points within the effective area of the substrate at the judgement point, even if the shot area subject to exposure is a chipped shot, the most appropriate detection points can be selected to control the rolling of the substrate.
With the first exposure apparatus according to the present invention, the selection unit may select the detection points to confirm detection results of the driving unit within the illumination area when the second type detection point selection criteria is set. In such a case, the selection unit selects the detection points that the driving unit uses for confirmation of control results within the illumination area on the substrate where the illumination light illuminates. Therefore, by using the detection results of the detecting points for confirmation, the control results of the position of the substrate in the optical axis direction and the tilt in the second direction can be accurately confirmed.
With the first exposure apparatus according to the present invention, when the second type detection point selection criteria is set, the substrate driving unit may control one of the position of the substrate in the optical axis direction, and a position of the optical axis direction and the tilt in the second direction. That is, the tilt of substrate in the first direction may not be controlled. In such a case, it becomes possible to precisely adjust the position of the substrate in the optical axis direction, and either the position in the optical axis position or the rolling, which greatly affect defocus; therefore, it becomes possible to prevent the critical dimension variation by a macroscopic observation, which is caused by defocus on exposure. In this case, so long as the position of the substrate in the optical axis direction and the rolling can be adjusted, alternate scanning can be performed on the entire shot area on the substrate, including the circumferential portion, thus allowing extremely high throughput to be maintained.
According to the second aspect of the present invention, there is provided a second exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system that has detection points which are capable of detecting positional information on the substrate surface in an optical axis direction of the projection optical system; an adjustment system which adjusts a positional relationship between an image plane of the projection optical system and the substrate surface based on detection results of the focus detection system; and a switching system that switches an operation of the detection points of the focus detection system located within an illumination area between controlling the adjustment system and confirming results of the adjustment performed by the adjustment system.
With this apparatus, as necessary, the switching system switches the detection points of the focus detection system located within an illumination area between controlling the adjustment system and confirming the results of control performed by the adjustment system. For example, when the switching system switches the detection points arranged within the illumination area to control the adjustment system, the adjustment system adjusts the positional relationship between the image plane of the projection optical system and the substrate surface. This adjustment is performed in accordance with the positional information on the substrate surface in an optical axis direction of the projection optical system detected at increased points. Thus, focus leveling control is performed which target surface is the averaged substrate surface of the uneven surface of the entire shot area subject to exposure. And, when the switching system switches the detection points from the adjustment system to confirming the results of control, focus leveling control is performed with priority on the tilt of substrate in the second direction which is perpendicular to the first direction. The first direction, is the moving direction of the substrate during relative scanning.
In this case, for example, the switching system can switch the detection points of the focus detection system arranged within an illumination area according to a type of pattern of the mask to be transferred onto the shot area subject to exposure. Or, the switching system can switch the detection points of the focus detection system arranged within an illumination area depending on whether the shot area subject to exposure is located at the circumferential portion of the substrate. In the former case, when the pattern to be exposed on the shot area subject to exposure is a circuit pattern of a system LSI having a CPU and a memory pattern, the detection points arranged in the illumination area can be switched to confirm the results of control. And when the circuit pattern is a memory circuit, the detection points can be switched to control the adjustment system. In the latter case, when the surface of the substrate is moderately even as with the shot areas located in the internal portion of the substrate, the detection points arranged in the illumination area can be switched to control the adjustment system. And when the surface of the substrate is fairly rough as with the shot areas located in the peripheral portion of the substrate, the detection points arranged in the illumination area can be switched to confirm the results of control.
According to the third aspect of the present invention, there is provided a third exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system that detects positional information on the substrate surface in an optical axis direction of the projection optical system which has detection points in a first row which is located before an illumination area of the illumination light, a second row which is located apart from the detection points in the first row in a moving direction of the substrate being a first direction during the relative scanning, and a third row which is located apart from the detection points in the second row in the first direction; a substrate driving system which drives the substrate in the optical axis direction and a tilt with respect to a surface perpendicular to the optical axis; a relative scanning unit which relatively scans the mask and the substrate with respect to the projection optical system; and a controller which controls the substrate driving system to adjust a positional relationship between an image plane of the projection optical system and the substrate surface based on detection results of the focus detection system, and the controller performs after relative scanning of the mask and the substrate is started by the relative scanning unit to transfer the pattern onto the shot area which is an inward and chipped shot, a first controlled state control which controls a position of the substrate in the optical axis direction by open control of the substrate driving system in accordance with detection results of the detection points in the first row when only the detection points come into an effective area of the substrate, a second controlled state control which controls the position of the substrate in the optical axis direction by closed control of the substrate driving system in accordance with detection results of the detection points only in the second row when the detection points come into the effective area of the substrate while the first controlled state control is performed, and a third controlled state control which controls the position of the substrate in the optical axis direction and a tilt in the first direction by closed control of the substrate driving system in accordance with detection results of the detection points in the first, second, and third row when the detection points in the third row come into the effective area of the substrate while the second controlled state control is performed.
With this apparatus, as soon as relative scanning of the mask and substrate starts with respect to the projection optical system to transfer a pattern onto an inward and chipped shot on the substrate, and the detection points only in the first row come into the effective area of the substrate, the main controller controls the substrate driving system by open control. By this open control, the position of the substrate in the optical axis direction is controlled, and thus the first state control is performed. That is, the substrate driving system is open controlled before the illumination area comes to the effective area of the substrate, therefore, the pre-exposing dynamic focusing of an inward shot can be accelerated. Also, while the substrate driving system is performing the pre-exposing dynamic focusing by open control, in addition to the detection points in the first row, when the detection points in the second row which are apart from the detection points in the first row in the first direction come into the effective area of the substrate, the main controller controls the substrate driving system by closed control based on the detection results of only the detection points in the second row. By this control, the position of the substrate in the optical axis direction is adjusted, thus the second state control is performed. That is, since the pre-exposing dynamic focusing is completed in the first state control, and the substrate driving system is then close-controlled based on the detection results of the detection points only in the second row, the focus can be controlled at high precision. The first direction, in this case, is the substrate moving direction on relative scanning.
Furthermore, while the focus is controlled by closed control, as soon as the detection points in the third row which are apart from the detection points in the second row on the opposite side of the detection points in the first row in the first direction come into the effective area of the substrate, the main controller controls the substrate driving system by closed control in accordance with the detection results of the detection points in the first, second, and third row. By this control, the position of the substrate in the optical axis direction and the tilt in the first direction is closed controlled, thus performing the third controlled state. That is, as soon as pitching control becomes possible, in addition to focus control, leveling (pitching) control in the first direction is performed. Accordingly, with the present invention, on exposing and inward and chipped shot, the position of the substrate in the optical axis direction, or, the tilt in the first direction (pitching) can further be precisely adjusted. Therefore, alternate scanning exposure can be performed on the entire shot area with the degree of contrast deterioration of the optical image due to pitching error suppressed at a minimum.
In this case, the controller may add a tilt in a second direction subject to open control when two of the detection points in the first row come into the effective area of the substrate, the second direction being a direction perpendicular to the first direction. In such a case, in addition to the pre-exposing dynamic focusing, the tilt of the substrate in the second direction (rolling), which is a cause of defocus, can also be brought to a proximate level.
In this case, the controller may change control of the tilt of the substrate in the second direction from open control to closed control in accordance with detection results of two of the detection points in the second row when the detection points come into the effective area of the substrate. In such a case, as soon as the pre-exposing dynamic focusing is completed and the rolling is brought to a proximate level, the position of the substrate in the optical axis direction and rolling can be closed controlled with high precision, thus can positively prevent defocus from occurring.
According to the fourth aspect of the present invention, there is provided a fourth exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system that detects positional information on the substrate surface in an optical axis direction of the projection optical system which has detection points in a first row which is located before an illumination area of the illumination light, and a second row which is located apart from the detection points in the first row in a moving direction of the substrate being a first direction during the relative scanning; a substrate driving system which drives the substrate in the optical axis direction and a tilt with respect to a surface perpendicular to the optical axis; a relative scanning unit which relatively scans the mask and the substrate with respect to the projection optical system; and a controller which controls the substrate driving system to adjust a positional relationship between an image plane of the projection optical system and the substrate surface based on detection results of the focus detection system, and the controller performs after relative scanning of the mask and the substrate is started by the relative scanning unit to transfer the pattern onto the shot area which is an inward and chipped shot, a first controlled state control which controls the substrate in the optical axis direction and of a tilt in a second direction which is perpendicular to the first direction to at least adjust a position in the optical axis direction by closed control of the substrate driving system in accordance with detection results of the detection points in the first row and the second row, a second controlled state control which performs adjustment of one of the position of the substrate in the optical axis direction and of the tilt in the second direction to at least adjust the position in the optical axis direction by closed control of the substrate driving system in accordance with detection results of the detection points in the second row when the detection points of the first row come off the effective area of the substrate while the first controlled state control is performed, and a third controlled state control which locks the control when the detection points in the second row come off the effective area of the substrate while the second controlled state control is performed.
With this apparatus, as soon as relative scanning of the mask and substrate starts with respect to the projection optical system to transfer a pattern onto an outward and chipped shot on the substrate, the main controller controls the substrate driving system by closed control in accordance with the detection results of the detection points in the first row before the illumination area, the detection points in the second row which are apart from the detection points in the first row in the first direction being the substrate moving direction, and the detection results of other detection points. By this control, the first state control which adjusts at least the position of the substrate in the optical axis direction between the position of the substrate in the optical axis direction and the tilt in the second direction which is perpendicular to the first direction, is performed. That is, at least the focus is controlled, in consideration of the prereading data. Therefore, phase delay of the focus can be suppressed, and at least focus control of the substrate can be performed with high precision.
During such a first state control, when the detection points in the first row come off the effective area of the substrate, the main controller drives the substrate driving system by closed control based on the detection results of the detection points in the second row, within or close to the illumination area. By this control, at least the position of the substrate in the optical axis direction is adjusted, between the position of the substrate in the optical axis direction and the tilt in the second direction. And, while in this second controlled state, when the detection points in the second row come off the effective area of the substrate, follow-up control of the position of the substrate in the optical axis with high precision becomes difficult, therefore, the controller performs the third controlled state. This locks the control so as to allow control based on target values that are constant, or vary in a predetermined manner. Accordingly, with the fourth exposure apparatus of the present invention, on exposing and outward and chipped shot, at least the position of the substrate in the optical axis direction can be controlled with the highest precision possible. Therefore, alternate scanning exposure can be performed on the entire shot area with the deterioration of the optical image due to defocus suppressed to a minimum.
According to the fifth aspect of the present invention, there is provided a fifth exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system that detects positional information on the substrate surface in an optical axis direction of the projection optical system which has detection points in a first row which is located before an illumination area of the illumination light, a second row which is located in the illumination area, and a third row which is located in the illumination area; a substrate driving system which drives the substrate in the optical axis direction and a tilt with respect to a surface perpendicular to the optical axis; a relative scanning unit which relatively scans the mask and the substrate with respect to the projection optical system; and a controller which controls the substrate driving system to adjust a positional relationship between an image plane of the projection optical system and the substrate surface based on detection results of the focus detection system, and the controller obtains a control error of the substrate driving system during relative scanning of the mask and the substrate by the relative scanning unit in accordance with detection results of the detection points in the first row and the second row at a first point where prereading of a distance between the detection points of the first row and the second row is performed, and the second row and the third row at a second point where an area of the substrate detected at the detection points of the first row comes to the detection points of the second row.
With this apparatus, while the relative scanning unit relatively scans the mask and the substrate, the controller obtains the control error of the substrate driving system. The control error is obtained according to the detection results of: the detection points in the first row located before the illumination area and the second row located within the illumination area at the first point where prereading of a distance between the detection points of the first row and the second row is performed; and the detection points in the second row and the third row at a second point where an area of the substrate detected at the detection points of the first row comes to the detection points of the second row. That is, when the controller secures no control delay in the substrate driving system, the detection results of the first row and second row at the first point serves as the detection results of the substrate driving system after the control has been preformed. If the distance between the detection points of the first and second row and the second and third row is equal, the difference between the detection results of the first and second row at the first point and the detection results of the detection points in the second row and the third row at a second point where an area of the substrate detected at the detection points of the first row comes to the detection points of the second row almost reflects the substrate driving amount from the first point to the second point. Accordingly, if the target value is constant, when the error to the target value at the first point is stored, the control error of the substrate driving system can be precisely obtained by simple calculation. This calculation is based on the detection results of the first and second row at the first point, the detection results of the second and third row at the second point, and the error to the target value at the first point. Therefore, the controller controls the substrate driving system according to the detection results of the focus detection system so that such control errors become zero, and thus the positional relationship between the image surface of the projection optical system and the substrate surface can be adjusted.
In this case, the control error may be obtained by the controller which stores a data of a difference between a target surface obtained by detection results of the detection points in the first, second, and third rows at the first point and the detection results of the first and second row, and compares the stored data with the detection results of the detection points in the second and third rows at the second point.
According to the sixth aspect of the present invention, there is provided a sixth exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system which can detect positional information on the substrate surface in an optical axis direction of the projection optical system at a plurality of detection points; and a substrate driving unit which in accordance with the positional information of a selected plurality of detection points serving as control purposes among the plurality of detection points drives the substrate in the optical axis direction and in a tilt direction to a surface perpendicular to the optical axis to adjust a positional relationship between the substrate surface within an illumination area and an image plane of the projection optical system, and rotates the substrate which has a rotational axis extending in a first direction as center and passing through the barycenter of a second direction in an arrangement of the selected plurality of detection points serving as control purposes, to control a tilt in the second direction being perpendicular to a first direction being a direction of the relative scanning.
With this apparatus, the substrate driving unit adjusts the positional relationship between the substrate surface within the illumination area and the image plane of the projection optical system by driving the substrate in the optical axis direction and in a tilt direction to a surface perpendicular to the optical axis. This adjustment is performed in accordance with the positional information regarding the substrate surface in the optical axis direction of the projection optical system of a selected plurality of detection points serving as control purposes among the plurality of detection points. Also, the substrate driving unit controls the tilt in the second direction by rotating the substrate which has a rotational axis extending in the first direction as center and passing through the barycenter of the second direction in an arrangement of the selected plurality of detection points serving as control purposes. The first direction in this case, is the relative scanning direction, whereas the second direction is a direction perpendicular to a first direction. Therefore, even in the case detection points with an asymmetrical arrangement are selected, the tilt of the substrate in the second direction can be adjusted without affecting the adjustment of the position of the substrate in the optical axis direction. Accordingly, detection points that can most effectively control the tilt of the substrate in the second direction can be selected for control purposes. Thus, this makes it possible to precisely adjust the position of the substrate surface in the optical axis direction and the rolling, which greatly affect defocus; therefore, it becomes possible to effectively prevent the critical dimension variation by a macroscopic observation, which is caused by defocus on exposure.
In this case, the substrate driving unit can control a position of the substrate in the optical axis direction and the tilt in the second direction so as to prevent interference between the position of the substrate in the optical axis direction and the tilt in the second direction.
With the sixth exposure apparatus according to the present invention, the substrate driving unit can further control a tilt of the substrate in the first direction by making the substrate rotate around a predetermined axis parallel to the second direction.
In this case, the substrate driving unit preferably controls a position of the substrate in the optical axis direction and the tilt in the first direction so as to prevent interference between the position of the substrate in the optical axis direction and the tilt in the first direction.
In this case, the substrate driving unit can set a target value of the position of the substrate in the optical axis direction in consideration of a correction value to remove the interference between the position of the substrate in the optical axis direction and the tilt in the first direction.
According to the seventh aspect of the present invention, there is provided a seventh exposure apparatus which relatively scans a mask and a substrate with respect to a projection optical system while the mask having a pattern formed is illuminated with an illumination light to transfer the pattern onto at least one shot area on the substrate via the projection optical system, the exposure apparatus comprising: a focus detection system which can detect positional information on the substrate surface in an optical axis direction of the projection optical system at a plurality of detection points; and a substrate driving unit which in accordance with the positional information of a selected plurality of detection points among the plurality of detection points drives the substrate in the optical axis direction and in a tilt direction to a surface perpendicular to the optical axis to adjust a positional relationship between the substrate surface within an illumination area and an image plane of the projection optical system, and switches detection points to be used in accordance with progress of control during the relative scanning.
With this apparatus, the substrate driving unit drives the substrate in the optical axis direction and in a tilt direction to a surface perpendicular to the optical axis to adjust a positional relationship between the substrate surface within an illumination area and an image plane of the projection optical system. This adjustment is based on the positional information of a selected plurality of detection points among the plurality of detection points. Also, the substrate driving unit switches the detection points to be used in accordance with progress of control during the relative scanning of the mask and the substrate. So, for example, by switching the detection points to be used so that a more precise focus control or focus leveling control can be performed in accordance with the controlled status, focus control or focus leveling control with high precision can be achieved.
In this case, the plurality of detection points can be respectively arranged within the illumination area illuminated by the illumination light and away from the illumination area in a first direction, the first direction being a direction of relative scanning, and the substrate driving unit can switch detection points to be used from the detection points away from the illumination area which serve control purposes to the detection points arranged within the illumination area which serve confirmation purposes in accordance with progress of control during the relative scanning. In such a case, when an inward shot is subject to scanning exposure, for example, by selecting the detection points away from the illumination area until the pre-exposing dynamic focusing is completed, the pre-exposing dynamic focusing can be performed without any control delay. And after the pre-exposing dynamic focusing is completed, by selecting the detection points arranged within the illumination area which serve confirmation purposes, focus control or focus leveling control can be performed with high precision while confirming the results of control.
Furthermore, in the lithographic process, by performing exposure with the exposure apparatus in the present invention, exposure can be performed with high precision, without any critical dimension variation by a macroscopic observation due to defocus, thus allowing a multiple layer of patterns with high overlay accuracy to be formed on a substrate. Accordingly, with the present invention, from another aspect, there is provided a device manufacturing method that uses the exposure apparatus of the present invention.